package com.ttai.untils;

import android.text.TextUtils;
import android.util.Base64;

import java.security.Provider;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class AesAndroid {
        private final static String HEX = "0123456789ABCDEF";
        private  static final String CBC_PKCS5_PADDING = "AES/CBC/PKCS5Padding";//AES是加密方式 CBC是工作模式 PKCS5Padding是填充模式
        private  static final String AES = "AES";//AES 加密
        private  static final String  SHA1PRNG="SHA1PRNG";// SHA1PRNG 强随机种子算法, 要区别4.2以上版本的调用方法

        /**
         * 生成随机数，可以当做动态的密钥 加密和解密的密钥必须一致，不然将不能解密
         */
        public static String generateKey() {
            try {
                SecureRandom localSecureRandom = SecureRandom.getInstance(SHA1PRNG);
                byte[] bytes_key = new byte[20];
                localSecureRandom.nextBytes(bytes_key);
                String str_key = toHex(bytes_key);
                return str_key;
            } catch (Exception e) {
                e.printStackTrace();
            }
            return null;
        }
        // 对密钥进行处理
        private static byte[] getRawKey(byte[] seed) throws Exception {
            KeyGenerator kgen = KeyGenerator.getInstance(AES);
            //for android
            SecureRandom sr = null;
            // 在4.2以上版本中，SecureRandom获取方式发生了改变
            int sdk_version = android.os.Build.VERSION.SDK_INT;
            if(sdk_version>23){  // Android  6.0 以上
                sr = SecureRandom.getInstance(SHA1PRNG,new CryptoProvider());
            }else if(android.os.Build.VERSION.SDK_INT >= 17){   //4.2及以上
                sr = SecureRandom.getInstance(SHA1PRNG, "Crypto");
            }else {
                sr = SecureRandom.getInstance(SHA1PRNG);
            }


            // for Java
            // secureRandom = SecureRandom.getInstance(SHA1PRNG);
            sr.setSeed(seed);
            kgen.init(128, sr); //256 bits or 128 bits,192bits
            //AES中128位密钥版本有10个加密循环，192比特密钥版本有12个加密循环，256比特密钥版本则有14个加密循环。
            SecretKey skey = kgen.generateKey();
            byte[] raw = skey.getEncoded();
            return raw;
        }

        /*
         * 加密
         */
        public static String encrypt(String key, String cleartext) {
            if (TextUtils.isEmpty(cleartext)) {
                return cleartext;
            }
            try {
                byte[] result = encrypt(key, cleartext.getBytes());
//            return Base64Encoder.encode(result);
                return new String(Base64.encode(result,Base64.DEFAULT));
            } catch (Exception e) {
                e.printStackTrace();
            }
            return null;
        }

        /**
         * 加密
         */
        private static byte[] encrypt(String key, byte[] clear) throws Exception {
            byte[] raw = getRawKey(key.getBytes());
            SecretKeySpec skeySpec = new SecretKeySpec(raw, AES);
            Cipher cipher = Cipher.getInstance(CBC_PKCS5_PADDING);
            cipher.init(Cipher.ENCRYPT_MODE, skeySpec, new IvParameterSpec(new byte[cipher.getBlockSize()]));
            byte[] encrypted = cipher.doFinal(clear);
            return encrypted;
        }
        /**
         * 解密
         */
        public static String decrypt(String key, String encrypted) {
            if (TextUtils.isEmpty(encrypted)) {
                return encrypted;
            }
            try {
//            byte[] enc = Base64Decoder.decodeToBytes(encrypted);
                byte[] enc = Base64.decode(encrypted,Base64.DEFAULT);
                byte[] result = decrypt(key, enc);
                return new String(result);
            } catch (Exception e) {
                e.printStackTrace();
            }
            return null;
        }

        /**
         * 解密
         */
        private static byte[] decrypt(String key, byte[] encrypted) throws Exception {
            byte[] raw = getRawKey(key.getBytes());
            SecretKeySpec skeySpec = new SecretKeySpec(raw, AES);
            Cipher cipher = Cipher.getInstance(CBC_PKCS5_PADDING);
            cipher.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(new byte[cipher.getBlockSize()]));
            byte[] decrypted = cipher.doFinal(encrypted);
            return decrypted;
        }
        //二进制转字符
        public static String toHex(byte[] buf) {
            if (buf == null)
                return "";
            StringBuffer result = new StringBuffer(2 * buf.length);
            for (int i = 0; i < buf.length; i++) {
                appendHex(result, buf[i]);
            }
            return result.toString();
        }

        private static void appendHex(StringBuffer sb, byte b) {
            sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
        }


        // 增加  CryptoProvider  类

        public static  class CryptoProvider extends Provider {
            /**
             * Creates a Provider and puts parameters
             */
            public CryptoProvider() {
                super("Crypto", 1.0, "HARMONY (SHA1 digest; SecureRandom; SHA1withDSA signature)");
                put("SecureRandom.SHA1PRNG",
                        "org.apache.harmony.security.provider.crypto.SHA1PRNG_SecureRandomImpl");
                put("SecureRandom.SHA1PRNG ImplementedIn", "Software");
            }
        }

    }
